1. Field of the Invention
This invention relates to a filter for an aquarium apparatus for keeping and displaying tropical fish or the like.
2. Description of the Prior Art
An aquarium apparatus consists of a tank, a lid, an illuminator, a filter, etc.
Of these components, the filter serves to physically and biologically filter out contaminants from the water contained in the tank.
The filter and illuminator are designed to constitute a lid covering the open top of the tank.
In the filter, water pumped from the tank with a pump mechanism is showered from a shower pipe or a trough onto a filter material provided in a filter unit accommodated in a filter tank casing.
The filter unit is configured to concurrently perform physical filtering for filtering out floating particles in the water using chemical fibers or other such filter material and biological filtering for filtering out organic substances dissolved in the water using bacteria living in a filter material such as gravel.
In the prior art filter for the aquarium apparatus, water is supplied to a filter unit by showering. This has the advantage of increasing the amount of dissolved oxygen available to the fish or the like in the aquarium tank.
However, showering also has the effect of reducing the amount of dissolved carbon dioxide available to aquatic plants in the aquarium tank.
This method of supplying water is therefore inappropriate for the filter of an aquarium apparatus used mainly to display aquatic plants.
Moreover, since the filter unit is configured to concurrently perform physical filtering and biological filtering, the biological filtering function is curtailed along with the physical filtering function when the filter material is removed for replacement after becoming clogged. It therefore becomes impossible to maintain satisfactory water quality through biological filtering even though the biological filtering function has not been reduced.
The object of the present invention is to preclude the above inconvenience by providing a filter for an aquarium apparatus which can be used irrespective of whether the apparatus is used to display fish or aquatic plants and which enables the biological filtering function to maintain satisfactory water quality even when the physical filtering function is not in effect.